Spontaneous attentional lapses are reflected in a positive voltage shift of the event-related potential in the P2 peak time window
The dynamic and constantly changing environment requires fast and selective sensory processing to maintain adaptive goal-directed behavior. Several classic studies of auditory attention revealed a negative voltage shift of event-related potential (ERP) within the 100 200 ms time window after stimulus onset in the attended channel compared with the unattended channel (Näätänen et al. 1978; Näätänen et al. 2011). This phenomenon was interpreted as an active top-down facilitation of relevant sensory representations. In the same time interval, Alho et al. (1987) found rejection positivity that can be elicited in response to actively ignored sounds, thus, reflecting processes of top-down suppression of irrelevant stimuli. Most of the studies in the field dealt with forced attentional manipulations, while the present study was focused on ERP correlates of spontaneous attentional lapses. We hypothesized that a positive ERP shift similar to the rejection positivity (Alho et al. 1987; Degerman et al. 2008) may be present during spontaneous failures to appropriately detect stimuli. The auditory condensation task was used: four target auditory stimuli that differed in two independent features were presented randomly with equal probability. Each sinusoidal tone was either 500 Hz (‘low’) or 2000 Hz (‘high’), either a pure tone (‘pure’) or the same tone intermixed with broadband noise. Control procedures ensured that each of the stimulus features could be easily discriminated by all participants. Participants were instructed to respond to each stimulus by pressing one of the two buttons according to a rule based on stimulus feature conjunction (see Table), which is a much more demanding task compared with singe feature discrimination (Novikov et al. 2015). In Experiment 1, participants were presented only with target stimuli. In Experiment 2 distractor stimuli were introduced in the sequence of targets. The relative probability ratio of these non-target-stimuli to all four equiprobable target stimuli (same as in experiment 1) pooled together was 4:1. In Experiment 1 (see Figure A), the positive ERP shift within the time window 120-240 ms (P2 peak of auditory ERP) was very robust for errors compared with correct responses (F1,51 = 24.516, p < .0001, ƞp2 = .325, 15 pericentral electrodes). In Experiment 2 (see Figure B), P2 was overlapping with N2 and less evident for target stimuli compared with Experiment 1. Within the P2 time range, ERP was shifted positively for errors compared with correct responses (F1,52 = 4.29, p = 0.04, ƞp2 = 0.08, 9 centro-parietal electrodes). In all the experiments presented here, the ERP within the P2 peak time window was shifted positively during attentional lapses compared with correct responses. This effect resembles the rejection positivity and supports the hypothesis that information processing is reduced preceding erroneous responses (Alho et al. 1987; Degerman et al. 2008); this is likely a consequence of misallocation of attention due to competition with other mental processes such as mind wandering. Importantly, the ERP correlate of spontaneous attentional failures presented here resembles the effect of inattention forced overtly (Degerman et al. 2008; Näätänen et al. 1978; Tong, Melara and Rao 2009). Thus, our finding supports the hypothesis that information processing is reduced during spontaneous attentional lapses leading to erroneous responses.